1. Field of the Invention
The present invention relates to a magnetic tape cassette. More particularly, the present invention relates to a novel compact cassette suitable for use with audio tape whose size is equal to or larger than the Phillips type.
2. Background of the Invention
With the recent tendency toward smaller and lighter cassette tape recorders, the use of smaller magnetic tape cassettes has expanded in video recording applications. In the area of audio recording, too, it is strongly desired to develop magnetic tape cassettes that are adaptive to high-quality and high-density recording and reproduction over long playing times. In response to this need, digital rather than analog tape cassettes have been proposed which depend on the principles of pulse-code modulation (PCM). In PCM, an input signal is converted to a train of pulses for recording and reproduction purposes. According to this system, the range of recording frequencies must be about 5 times as wide as in the case of the conventional audio tape and it is common practice today to use large-size video tape cassettes that are capable of recording over a broader frequency range than audio compact cassettes.
Except in special cases, the video cassettes of the type described above are designed to allow recording with a rotary head. The basic feature common to these cassettes is that the opening in the front portion is closed while there is provided a guard panel that is upwardly openable. In other words, in digital recording which uses shorter wavelengths than the conventional audio compact cassette and which is intended to perfrom high-density recording and reproduction over a wide frequency band, the cassette must be so constructed that is achieves sufficient tape protection to ensure high reliability.
The present invention aims at providing a magnetic tape cassette that is adaptive to audio recording and reproduction over a wide frequency band which is comparable to the range used for the video tape cassette described above. The size of this tape cassette is very small and is by no means larger than the conventional audio compact cassette.
Conventionally, a magnetic tape cassette of the type contemplated by the present invention has incorporated therein a magnetic tape that is wound around a flangeless hub to which is secured a leader tape that is continous to the end of the magnetic tape. The hub is composed of a hollow cylindrical core that has a girdle with a cutout portion formed around it and a clamp that engages the cutout to hold the leader tape in position. The clamp is elastic so that it will tightly engage with the cutout portion. The clamp is so shaped that it has a different curvature than the girdle and, when fitted into the hub, the clamp deflects in such a manner that its curvature comes into registry with the curvature of the girdle. In fact, however, the clamp is retained with the hub by being elastically fitted into the cutout portion in a very tight state, so that the curvature of the clamp fitted into the cutout seldom completely registers with the curvature of the girdle. As a result, the hub becomes cut-of-round or eccentric (not completely round) and the running property of the magnetic tape wound onto the hub is adversely affected, as manifested by erratic tape running.
If the clamp was molded to have a curature that is equal to that of the girdle with the other features of the cassette construction remaining the same, the clamp would not be tightly fitted into the cutout and would be offset as a result of sliding in the axial direction. In an extreme case, the clamp would become completely dislodged from the cutout, thereby failing to hold the leader tape in position.